1. Field of the Invention
The invention relates to a steering system.
2. Description of Related Art
There has been proposed a steering system including a telescopic mechanism constituted by an outer tube and an inner tube that are fitted to each other so as to be slidable relative to each other, wherein the steering system has a telescopic lock function of restricting relative slide movement in the telescopic mechanism, and wherein a single eccentric cam, which is rotated together with a lock shaft in accordance with the operation of an operation lever, presses an outer periphery of the inner tube through an opening formed in the outer tube so as to achieve telescopic lock. For example, refer to Japanese Patent Application Publication No. 2008-132819 (JP 2008-132819 A) and Japanese Patent Application Publication No. 2010-30579 (JP 2010-30579 A). In the steering system described in JP 2010-30579 A, a balance spring is provided for supporting the weight of a steering column at the time of unlocking, in order to assist tilt operation. One end of the balance spring is locked to a fixing bracket that is secured to a vehicle body, and an abutting portion of the balance spring abuts on a ring fitted to an outer periphery of the eccentric cam. The balance spring urges the steering column in an upward tilt direction through the eccentric cam and the lock shaft that is rotated together with the eccentric cam.
However, there is a possibility that a force for maintaining the locked condition may be weakened at the time of locking, due to variation in dimensional accuracy among individual components. In more detail, the rotation angle position of the eccentric cam varies at the time of locking, due to the variation in dimensional accuracy among individual components. Accordingly, the direction of load due to the torque for rotating the operation lever varies, and thus, a push-up force applied by the eccentric cam varies. As a result, there is a possibility that a required push-up force may not be obtained.
A plurality of rings which are to be fitted to the eccentric cam, and which have different outer diameters in multiple specifications may be prepared, and a specific one among these rings in the multiple specifications may be selected for an individual steering system so that the eccentric cam can be held at an appropriate rotation angle position, and a required push-up force, that is, a required maintaining force can be obtained. In this case, however, a component cost and an assembly cost are increased, and as a result, a manufacturing cost is increased.